In recent years, a home-electric-appliance cooperation function has been introduced for a home network, with which various home electric appliances are connected to a network by a home energy management system (HEMS) having a function of managing power usage for addressing an environmental issue, turning power on/off from outside a house, and the like, in addition to cooperation of AV home electric appliances by internet protocol (IP) connection using Ethernet® or wireless local area network (LAN). However, there are home electric appliances whose computational performance is insufficient to have a communication function, and home electric appliances which do not have a communication function due to a matter of cost.
In order to solve such a problem, Patent Literature (PTL) 1 discloses a technique of efficiently establishing communication between devices among limited optical spatial transmission devices which transmit information to free space using light, by performing communication using plural single color light sources of illumination light.